Structural frame assemblies that use extruded metallic or other rails as structural members are known and are widely used as supports or fixture components with automation equipment, as well as for furniture and building components. Such components, for example, rails, are typically held together at a joint with threaded fasteners that include bolts that extend orthogonally or in a normal direction with respect to rails and which are received into nuts, captured nuts, and/or threaded inserts, to make and maintain respective interconnections at the joint. However, bolts, captured nuts, and/or threaded inserts which rotate with respect to each other may loosen over time when the joint is subjected to vibration or loaded and unloaded during use.
The present inventor has recognized that in known frame assembly systems, assembly and aligning procedures can be frustrating because components at each joint can freely pivot or otherwise substantially move with respect to each other. The inventor has also recognized that such movement is typically created by pivotal movement of joint components about axes of pivotation that are defined by the fasteners that extend entirely orthogonally through the joint components and into rails. The inventor has recognized that movement of components at one joint is translated into movement of all other components that are connected directly or indirectly to the joint. The inventor has further recognized that when adjusting one corner in such a known system, the other corners or other components tend to become misadjusted and that this may make precision setups of such systems impractical or impossible. The present inventor has recognized that after a frame assembly is built, during use in some applications, joints tend to loosen so frequently that users may pin or weld the joints to try to increase the amount of time between adjusting of the frame assembly.
The present inventor also has recognized that in structural frame assemblies that use threaded fasteners to connect rails to each other, tightening the threaded fasteners may distort the rails. The present inventor has also recognized that when tightening threaded fasteners in rails that have longitudinally extending channels, the nuts, captured nuts, and/or threaded inserts engage portions of the rails that cause opposing sides of the rails to bend outwardly away from each other, distorting the rails by flaring out the rails at the joints.
The present inventor has further recognized that some joint looseness may be attributable to load-induced bolt elongation and/or thread wear of threaded fasteners, whereby, in joints having bolts that extend orthogonally or in a normal direction with respect to rails, the amount of looseness may correspond to the sizes of clearances that are created in the joints that correspond in size to the amount of elongation of the bolt or the amount of thread ware. The present inventor has recognized that joint looseness attributable to bolt elongation and thread wear may be relatively reduced by providing bolt assemblies having bolts that angularly or non-orthogonally intersect an interface defined by abutting surfaces of components being joined to each other at the joint. The present inventor has recognized that an amount of clearance that may be gained in a joint due to bolt elongation or thread wear may instead correspond to a vector component of such elongation or thread wear that aligns orthogonally or in a normal direction with respect to the interface between abutting surfaces of the components being joined to each other at the joint.
Therefore, it is a primary object and feature of the present invention to provide a structural frame assembly that has joints with mechanical interfaces that engage each other so that joint components mechanically align themselves while being tightened. This may provide a structural frame assembly that, during tightening of fasteners and without manual measuring and adjusting, automatically self-aligns with a relatively high amount of precision. This may also provide a structural frame assembly that can be precisely assembled, for example, with rails that lie precisely in common planes and rails that precisely intersect at 90°, or other angle(s) based on the particular configuration of a corner bracket being used, by merely tightening fasteners at joint locations. This may also provide a structural frame assembly with accuracy and precision of its end use dimensions being limited as a function of the accuracy and precision of the dimensions of the individual components of the structural frame assembly; and substantially not being limited by the skill of the assembler in accurately and precisely manually aligning the components. This may allow relatively less skilled assemblers to assemble highly precise structural frame assemblies and to do so relatively quickly. This automatic and self-aligning capability of the various components may also allow the joints of the structural frame assembly to restore to their precisely fitted positions or “return to zero” when the structural frame assembly enters a relaxed state after being subjected to loads and/or vibration. This may prevent the structural frame assembly from being skewed out of its precision setup position during use by absorbing loads primarily through, for example, bending of rails instead of face-to-face pivotal slip of components, about orthogonally extending fasteners, at joints. This may also allow the interfacing components of the joint assembly to further seat against each other during use while being subjected to loading, unloading, and vibrations, in preference to pivoting out of alignment, which may enhance or at least maintain the alignment integrity of the joint.
In accordance with another aspect of the present invention, a structural frame assembly is provided with joints that include brackets that may angularly accommodate bolts, non-orthogonally, with respect to abutting surfaces of a stack of components being joined to each other at the joint. This may provide a structural frame assembly that is highly rigid, resists fastener loosening, is relatively less susceptible to joint losing attributable to bolt elongation and thread wear, and has components that can be reused. This may allow the structural frame assembly to be used with automation equipment, for example, for incorporation into blanking stations or other uses for building blanking tools, that can be reconfigured and reused with a subsequent tool after a tool has been retired from service while providing precise component fitment and dimensional stability during use.
In accordance with another aspect of the present invention, a structural frame assembly is provided that includes a rail with a pair of abutment walls that are spaced from each other and extend angularly down and away from an outer surface of the rail, toward a middle portion of a cavity that extends longitudinally through the rail. A nut having a pair of shoulders and a pair of sidewalls that extend from the shoulders is held in the cavity. The shoulders of the nut may engage the abutment walls of the rail and at least one of the sidewalls of the nut may be spaced from the rail, defining a clearance therebetween. A bolt may extend angularly through the rail and operatively engage the nut so that rotating the bolt angularly advances or regresses the nut through the cavity. This may allow the shoulders of the nut to engage the abutment walls of the rail in multiple steps, by engaging one of the nut shoulders and a rail abutment wall adjacent the clearance between the nut sidewall and rail, allowing the nut to pivot within the cavity and about an edge defined at an end of the rail abutment wall so that the nut pivots until the second nut shoulder engages a second abutment wall at an opposing side of the cavity. The shoulders of the nut and the abutment walls of the rail may be angled so that further tightening of the bolt after the shoulders engage the rail abutment walls may draw the nut nearer to the outer surface of the rail and may also, by way of inwardly directed wedging action between interfacing surfaces of the shoulders and abutment walls, transversely compress the rail. This may allow tightening of a bolt to provide multi-axial tightening of the joint within the structural frame assembly by providing a clamping force in a direction that is normal to interfaces between various components to squeeze such components together within the joint and to transversely compress a rail at the joint location of the structural frame assembly.